Seasonal microbial community dynamics in a flowerpot-using personal composting system for disposal of household biowaste.

Abstract

Microbial community dynamics in a flowerpot-using solid biowaste composting (FUSBIC) process were monitored seasonally by quinone profiling and conventional microbiological methods. The FUSBIC system, which consisted of three flowerpots (14 L or 20 L capacity) with 5-6 kg each of a soil-compost mixture (SCM) as the primary reactors, was loaded daily with household biowaste from November 1998 to October 1999. The monthly average waste reduction rate was 88.2% for the 14-L system and 92.5% for the 20-L system on a wet weight basis. The direct total microbial count detected in the 14-L primary reactors ranged from 4.5 to 9.6x10(11) cells.g(-1) of dry wt of SCM, and the viable count of aerobic heterotrophic bacteria recovered on agar plates at 28 degrees C varied from 1.9 to 5.7x10(11) CFU.g(-1) of dry wt. The quinone content of SCM samples from the 14-L and 20-L systems ranged from 160 to 353 nmol.g(-1) of dry SCM. Ubiquinones, unsaturated menaquinones, and partially saturated menaquinones constituted 15.0-36.4, 14.8-22.0, and 41.8-61.6 mol% of the total content, respectively. The major quinone types detected were usually MK-8(H(2)), MK-9(H(2)), and Q-10. Variations in quinone profiles were evaluated numerically by using two parameters, the dissimilarity index (D) and microbial divergence index (MD(q)). The upper limit of seasonal changes in the microbial community structure was about 30% as expressed by D values. The MD(q) values calculated ranged from 18 to 22. A significant positive correlation was found between seasonal temperature and bacterial populations containing partially saturated menaquinones. These results indicated that the FUSBIC system contained highly diverse microbial populations that fluctuated to some extent depending on seasonal temperature. Members of the Actinobacteria were suggested to be the major constituents of the total population present.